The protein chemistry, the reaction mechanism and the specificity of phospholipase A2 from Crotalus adamanteus venom will be investigated. The dissociation of the dimeric enzyme into subunits and the physical and catalytic behavior of the enzyme in organic solvents, at the air-water and lipid-water interfaces will be determined. The kinetics of the enzyme-catalyzed hydrolysis of phospholipids and their analogs in water, organic solvents and at interfaces will be measured by interfacial tension, surface potential, pH-stat and spectroscopic techniques. The existence of covalent enzyme-substrate intermediates will be studied by kinetic analysis and by correlating substrate structure with enzymatic reactivity. The structure, specificity and mechanism of action of the acidic protease inhibitor from pineapple stem will be studied by kinetic methods, protein modifications and structural analysis.